A composition (10) for medical applications and a preparation method therefor, the composition (10) including at least one magnetic nanoparticle (100) comprising a nanodiamond (110) and at least one magnetic element (120), said at least one magnetic element (120) being embedded in the at least one nanodiamond (110) by means of an ion implantation system (400). The nanodiamond (110) may be synthesized with different components so as to improve the medical efficacy of the described composition (10).